I see. Browsing my German dictionary I found that in German they say "wievielte" or "wievielste(expecting more than 20)", literally meaning "how-many-eth". I wonder if there wasn't an Anglo-Saxon equivalent?

In Dutch we can say 'hoeveelste' as in German. I've always considered it a lack in the language of the English, who have more different numbers than names as it comes to kings, that you can't easily say: Henry the so-many-eth (Henry de zoveelste) when you're not sure which of the eight it is.